► Muscles often work in pairs which work against each other. These are called antagonistic pairs.
► The two muscles, the biceps and triceps are working against each other.
►When the biceps contracts the lower arm is raised and the arm bends. In this position the triceps muscle is relaxed.
► To straighten the arm the reverse happens. The triceps contracts straightening the arm, while the biceps relaxes.

Calorimeter:
(i) A calorimeter is a device used to measure the amount of heat gained or lost by a substance.
(ii) It consists of a vessel made up of metals like copper or aluminum which are good conductors of heat and electricity.
(iii) The metallic vessel is kept in an insulating jacket to prevent heat loss to the environment.
(iv) There are two holes in it. Through one hole a thermometer is inserted to measure the temperature of the contents.
(v) A stirrer is inserted through another hole for stirring the content in the vessel.
(vi) The vessel is filled with liquid which is heated by passing current through the heating element.
(vii) using this device we can measure the heat capacity of the liquid in the container.

(i) Computer is an electronic device that process the data and information according to our needs.
(ii) It follow instructions, called programs which determine the tasks the computer will perform.

S.No	Aerobic	Anaerobic
1.	Aerobic respiration takes Place in the presence of oxygen	6139robic respiration takes place in the absence of oxygen
2.	The end products of aerobic respiration are CO2 and H2O	The end products of anerobic respiration are CO2 ethanol and lactice acid
3.	Common in all higher Plants and animals	Common in certain micro organisms and human muscle cell

Agar Agar:
1. Agar Agar is extracted from some red algae namely Gelidium, Gracillaria etc
2. which is used to prepare growth medium in laboratories.
Algae in space travel:
1. Chlorella pyrenoidosa is used in space travel to get rid of Co, and decompose human wastes
Single cell protein (SCP):
1. Some of the single cell algae and blue green algae are used to produce protein.
2. Eg: Chlorella, spirulina

A chemical that kills or inhibits the growth of micro organism and is used to treat infections. The antibiotic penicillin was obtained from the fungi Penicillium chrysogenum. It is used to treat diseases such as tetanus and diphtheria.

S.No	Property	Metal	Non - metal
1	Malleability	Good	Poor - usually soft or brittle
2	Ductility	Good	Poor - usually soft or brittle
3	Melting point	usually high	usually low
4	Conductivity (Thermal and electrical)	Good	Very poor

The distance between the pole and the principle focus is called focal length (f) of a spherical mirror.

i)Pour soap powder or oil into the sea near their ship.
ii) It decreases the surface tension of sea water.
iii) It reduces the impact of the violent water current.

1. FPS - system (Foot -length, Pound - mass and Second - Time).
2. CGS - system (Centimetre -length, Gram - mass and Second - Time).
3. MKS - system (Metre - length, Kilogram - mass and Second - Time)·

(i) The primary hormones that regulate reproduction are the steroids such as androgens, estrogens and progesterone which have masculinizing, feminizing and gestational effects respectively.
(ii) These hormones are secreted from the gonads which are regulated by the anterior pituitary.
(iii) In male and female, reproductive behaviour and reproduction are mainly under the control of LH and FSH.
(iv) LH stimulates the testes to produce androgens, the male sex hormone
(v) Sperms are then actively produced.
(vi) In man sperm production starts at sexual puberty a4d may continue throughout his life.
Follicle stimulating Hormone (FSH)
(i) FSH in the female influences the development of the Graafian follicle and secretion of estrogens.
(ii) In the male it is necessary for the development of seminiferous tubules, and for spermatogenesis
Luteinizing Hormone (LH)
(i) In the female, it is the hormone necessary for ovulation, and the secretion of the luteal hormone Progesterone, and for the final maturation of the Graafian follicle
(ii) In the male it stimulates the interstitial (Leydig) cells of testes and the secretion of testosterone, and is referred to as the Interstitial cell stimulating Hormone (ICSH).
Prolactin (PRL) or Lactogenic Hormone:-
The main function of this{ormone is milk secretion during lactation.
Oxytocin Hormone:
Oxytocin causes expulsion of milk from the breast and it is also involved in the contraction of some muscles of uterus during child birth

a) Aluminium Sulphate - Al₂(SO₄)₃
b) Silver Nitrate - AgNO₃
c) Magnesium Oxide - MgO
d) Barium Chloride - BaCl₂

When a limited amount of CO₂ is passed through lime water, it turns milky due to the formation of insoluble calcium carbonate.
\(\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{CO}_{2} \rightarrow \mathrm{CaCO}_{3}+\mathrm{H}_{2} \mathrm{O}\)
When an excess amount of CO₂  is passed through lime water, it first turns milky and the milkiness disappears due to the formation of soluble calcium hydrogen carbonate Ca(HCO₃)₂.

Electroscope:
An electroscope is a scientific instrument used to detect the presence of electric charge on a body.
Types:
There are two types of electroscope.
a) Pith-ball electroscope
b) Gold-leaf electroscope.
Principle:
It works on the principle that like charges repel each other.
Structure of a gold leaf electroscope:
It is made up of a glass jar. A vertical brass rod is inserted into the jar through a cork. The top of brass rod has a horizontal brass rod or a brass disc. Two gold leaves are suspended from the brass rod inside the jar.
Working -
i) If a negatively charged object is brought near the top disc of the electroscope, it causes free electrons in the electroscope to move down into the leaves, leaving the top positive. Since both the leaves have negative charge, they repel each other and move apart.
ii) If a positive object is brought near the top disc of the electroscope, the free electrons in the electroscope start to move up towards the disc. The bottom has a net positive charge. The leaves repel other and move apart.

Burning fossil fuels is a cause of global warming because it produces Co, and methane. These gases give the greenhouse effect. This increase the Earth's average temperature and results in the phenomenon called Global warming.